Flexible stainless steel sutures



March 17, 1964 D. KAUFMAN- ETAL 3,125,095

FLEXIBLE STAINLESS STEEL suTUEEs Filed Nov. 1, 1961 M'M www# mu ,M0 #in United States Patent poration otMalne ,Face Nov. 1, 1961 ser. No. '149,449 7 claims. (ci. 12s-sass) This invention relates to a clean stainless steel surgicai suture having great strength, flexibility, and inertness built up of at least 19 individual stainless steel filaments with each filament having a diameter of less than about 0.0018 inch and which suture may additionally have an adherent thin impermeable layer of polytetrafiuoroethyiene thereon; and the ends of the suture may be exposed to act as an electrical conductor in heart surgery; and to a method of manufacturing such sutures.

Surgical sutures are, in general, of two maior classes, one absorbable which is absorbed by the body tissues and the second non-absorbable sutures which remain inert in the tissues. Sometimes it is necessary that such non-absorbable sutures have great strength and sometimes it is desirable that this suture be an electrical conductor. in the past individual metallic filaments have been used and where greater flexibility is desired, a plurality of' individual filaments have been spun into a wire. Usually seven filaments have been spun into a suture wire. Such a wire is more flexible than a monofilament wire of equivalent strength but does not have the flexibility required for certain usages. For surgical purposes it is desirable that a suture be sufilciently flexible that it may be easily tied in knots, including the surgeon's knot, and that the knot strength, that is, the pull over a knot, be as nearly as possible that of the straight suture. Additionally, it is desirable that the suture be flexible. For some uses, such as in heart surgery, it it desirable that an electrically conductive insulated suture be provided which carries an electric current to a specific area in the heart and that an electrical puise be given to this area of the heart (ventricular myocardium) when it is desired for the heart to beat. inasmuch as the heart should beat about 60 to 90 times per minute, and an electric impulse is needed for each heartbeat for the remaining life of the patient, an electrically con duetive suture for this purpose must be extremely flexible and must not work harden or become brittle under long continued flexing. In some instances a failure of the actuating impulse through the suture Awire can resuit in the loss of the patient. At the same time it is important that he insulating sheath remain intact so that electric impulses are not given to extraneous tissue areas. Whether the hare wire suture or the insulated suture is used, it is desirable that the suture have n minimum of capillarity so that tissue liquids are not conducted 4along the suture. and pathogenic organisms cannot spread through the suture, with serious results.

it is alsoA necessary that the suture have ancedle so that the.suture may-be readily inserted. Preferably. an eyeglass needle, as for example, a needle with a drilled hole in the rear end, is used. The end of the suture must be inserted into lthe hole in theend of the needle. it in cutting thewire forming the suture the filaments spiay, the end ofthe wire cannot be inserted vin the hole in the needle.

.preferred ythat eachindividual lment' have a diameter of not..greater than :about 0.00l8.,ineh. ,The l standard suture sizes in the United Statcsfare as prescribed by I 3,125,095 Patented Mar. 17, 1964 the United States Pharmacopeia and for non-absorbable sutures are:

Suture size Non-absorbabie suture,

USP designation: diameter in inches 6-0 0.002-0.004 5-0 0.0040.006 4-0 0.0060.008 000 0.008-0.0l0 00 ODIO-0.013 0 0.0i3-0.0i6

For such sutures in the smaller sizes such as 5-0, the individual filaments or ends may be twisted directly to form the muitifilament wire or suture. For the larger sizes, such as 4-0 and larger, it is preferred that a plurality of filaments or ends be twisted into strands or piys and a plurality of such strands or piys be twisted to form the wire, which is cut into segments forming the sutures. lt is prcferred that the filaments forming the strands have a twist or iny in a direction opposed to the twist or lay of the strands forming the wire. Thus the individual filaments tend to remain together rather than spiaying when the wire is cut. It is convenient although not necessary that the filaments have a left twist to form a strand and that the strands have a right twist to form a wire. The following table shows first the number of strands, and second the number of filaments in each strand, and third the diameter of each filament in inches, and the number ot' turns per inch for preferred sutures which meet U.S.P. size requirements. (Two alternative constructions are shown for a 4-0 size suture):

U.S.l. size Construction Turns perlnch i' x 7 x t) 00H 0 Hl 'xlxOOtlll ll 4-0 l0 x0.t)0lll ll 5-0 lil xt).00l2 l2 The number of turns per inch shown is a preferred value, but can vnry considerably, at least one or two turns per inch, and give good sutures. The diameter of each filament may vary some if other adjacent filaments have corresponding variations in the opposite direction so that the total cross section of thc filaments give the desired overall diameter.

One of the big problems in multi-filament construction is the cleaning of filaments. For surgical purposes it is obviously necessary that the suture be sterile at the time of use and it is highly desirable that it be ns clean ns possible.

it has-been found that n multi-filament stainless steel wire may be eiectrolytically cleaned to the required standnrds.` lt is surprising that even though much of thc dirt and grcnse associated with n drawing operation may be deep down inside the wire, an clectrolytic cleaning process evolves sufficient gas that particles of dirt and other contaminants are flushed out of the wire and clean wire is obtained without undue etching or size reduction.

After the anodic cleaning, the wire is washed and rinsed to,rcmove any of the electrolyte. Abath of dilute volatile minerai acid such as hydrochloric or nitric assists in dissolving any precipitated iron salts, and. on rinsing `with water, most of the acid is removed, and that which is notrcmoved by the rinse is .volatile and evaporates during drying.

The clean wire may be used as an uninsulated surgical suture.

Insulating ACoating For heart work where electric impulses are to be conducted, the surface of the wire is coated with an incr'.- polymer. Although polyethylene, polypropylene, nylon, etc. give good insulation, a thin layer of polytetraiiuoroethylene (frequently sold as Teflon), gives an excellent coating. and is preferred. The polytetrafluoroethylene may be applied by wrapping a thin spiral of tape about the wire, or it may be deposited in the form of an emulsion. One form of emulsion deposition is disclosed in U.S. Patent 2,977,748, Zisman'and FitzSimmons, Lubricated Wire Rope. In this patent each individual wire is shown as coated with sintered polymer to act as a lubricant. Itis here preferable that the entire multifilament wire be given a single coating. A single coating on the outside allows the transfer of current from filament to filament should one filament be ruptured, gives a smaller diameter insulated suture. and more effectively inhibits the flow of liquids by capillarity along the suture.

The polytetrafluoroethylene coating is removed from that portion of the multi-filament wire to which needles are to be attached by scraping or stripping.

Cutting the Wire Y It has been found that to cut the multi-filament wire without splaying the ends requires special techniques. The wire, essentially unstretched, may be cut without splaying by placing the wire on a ceramic anvil and contacting the wire with a pair of arc cutting electrodes which are conveniently tungsten electrodes which are spaced a few thousandths of an inch apart, for example, 0.005 inch apart and which are pressed down against the wire supported by the anvil to insure good contact. A comparatively high current is then passed between the electrodes which nrc cuts the wire. The voltages for cutting the wire, using an alternating current from an adjustable voltage transformer are conveniently:

lf the current transformer is an auto-transformer, care should be used to be sure that the current is drawn from the grounded side to avoid shock hazards.

The wire is kept straight as the current is applied and the heating and electric arc formed tends to fuse the end of the wire together without splaying. A height block is conveniently used to avoid undue pressure on the wire which might deform the wire when being contacted with the tungsten electrodes.

The formation of a large round bead which is too large to lit into the end of the needle indicates that too much voltage has been used. A thinly tapered fused end indicates the wire was under too much tension as it was cut. A flattened or oval fused end indicates that the wire was under too much pressure as it was beingV cut. lf the wire shows a burned arca but is not cut, either the electrodes were not in contact with the wire or too low a voltage was used. When correctly cut a small bead is formed which does not enlarge the diameter ot the wire and the individual filaments do not splay, and the end of the wire may be easily inserted into a drilled end needle. After being eut the ends of the'wire are lnsertedinto drilled-end needles of any1desired shape Aand size and' crimped into the needle in accordance with conventional techniques. The sutures may then 'be wound on a reel, packaged, heat sterilized or sterilized by use of s gaseous sterilant such as ethylene oxide or beta-propiolactone, or radiation, as for example gamma rays, and shipped.

Convenientlypboth ends of the suture are needled so that in heart operations one needle may beused to insert the bare end of the suture in the desired area of the heart (myocardium) and the other end of the needle may be used to pierce the chest wall and lead the suture to the skin surface of the patient for the attachment of a pacemaker" which applies a suitable electric pulse at suitable intervals to actuate the heart muscles. Surgically, it is desirable that the wire extend without sharp bends from the heart and that sufficient slack be left in the wire that no tension lis'applied to the wire and the wire does not tend to eut into body tissues during any physical activity in which the patient may subsequently participate.

Having described the general features of the invention, it may be better understood with reference to a specific example and t-he accompanying drawings in which:

FIGURE 1 is a view of a completed suture with a needle at each cnd.

FIGURE 2 is a view in partial section of a completed suture of 7 x 7 ply construction having polytetrailuoroethylene insulation.

FIGURE 3 is a cross section 'view taken through the crimped end of the needle and the end of the suture showing how the end of the are cut suture easily fits into and is crimped in a drilled-end needle. 'Ihe figure is a line drawing adapted from a photomicrographic.

FIGURE 4 is a view of the anodic cleaning and wash ing apparatus in diagrammatic form.

FIGURE 5 shows the wrapping of the wire with poly tetrafluoroethylene tape.

FIGURE 6 shows the electric cutting of the wire into individual sutures.

For a size 0 U.S.P. multi-lamcnt stainless steel wire, type 316 stainless steel was drawn to individual filaments 0.0018 inch in diameter. 7 such filaments were twisted to the left to form a strand and 7 such strands were twisted to he right to form a wire which consists of the 7 x 7 x 0.0018 inch construction. As shown in FIGURE 2 the wire 13 is formed of 7 strands or plys 12 Aeach formed of 7 individual filaments ll. About 8 turns per inch gives a conveniently tight construction.

As shown in FIGURE 4 such a wire is passed by pulley 14 into an anodic cleaning bath l5 which conveniently consists of about 85% phosphoric acid. Other convcntional acid anodc cleaning baths may be used. A voltage of about 9 to l0 volts gives a good cleaning. About 2.1 amperes flows, but varies with size of wire, about 0.6 ampere flows in a 5-0 wire.

The pulley' at each end feeding the wire down into the bath is of stainless steel, and each serves as a cur- -rent feed point. Y With a 5 foot long anodie cleaning bath, a speed of l2 feet per minute can be used. A longer bath can be used at higher speeds and the amount of elcctropolishing or anodic cleaning required depends -in part on the amount of dirt or contamination on the wire. The wire after being anodieally cleaned is passed through a 3 foot wash bath 16, which conveniently contains dilute, 6 normal nitric acid and then through a 6 foot rise bath 17 containing water. The wash and rinse baths are preferably hot, about C., to speed the rinsing. The wire is then dried by heating.

A convenient test for cleanness is to clamp the wire between two thicknesses of clean white muslin, clamped between a metal block and a rubber block, about 0.75 inch wide, under such pressure that a force of 0.5 pound is required to pull the wire through the muslin, and pull 20 inches of the wire slowly between the muslin layers. Any dirt on the wire is wiped oit' on the muslin. Conventional suture wire shows a black line on the muslin. Wire cleaned as above shows little or no marking on the muslin. A microscope may be used to'distinguish between dirt on the muslin and t-hreads cut by the wire, if any.

lt is preferable that the wire be untouched by human hands and protected from contamination until wrapped by a tape of polytctralluoroethylene. A single layer of tape about 0.006 inch thick or two layers each about 0.003 inch thick gives a good insulation. The wrapped wire is heated in the oven 19 until the tape is fused as a single layer of polytetrafluoroethylene 18, which partially penetrates into the wire.

Alternatively the poiytetrafluoroethylene coating may be applied as an emulsion which is dried and sintcred on to the wire.

A heated smoothing die mayl be used to smooth the coating on the wire.

The polytetrafluoroethylene coated wire has about a 6" segment of the coating scraped or stripped from the wire at suitable intervals. 36" intervals give 3 suture lengths which are frequently preferred. As shown in FIGURE 6 the bare wire is placed on a ceramic block 20 and tungsten electrodes 21 spaced about 0.005 inch apart are brought down on to the wire and the switch 22 closes to pass a cutting and fusing current through the wire and are cuts the wire.

The ends of the wire are inserted into the drilled-end needles 23 which needles are crimped about the wire. FIGURE 3 shows diagrammaticslly the crimping of the needle, the interior serrations on the drilled end needle and the way in which the are cutting of the wire tends to cause the end of the wire to shrink together so that it may be easily inserted in the drilled-end needle.

The insulated suture is shown at 24 with the polytetrafluoroethylene coating 18 on the wire 13, the ends of which are exposed so that they may be more easily crimped in the needles and to give an area for electrical contact.

Samples of various size sutures were tested in a M.l.l`. paper folding test machine, in which the specimens were folded through a sharp angle of 270', at 175 double folds per minute (at 73 F. and 50% R.H.) under' tension of 0.5 and 1.0 kilogram as compared with conventional sutures of seven single strands construction, folds to failure were:

The size -0 suture is too small for such a test to be significant.

Having thus described certain embodiments thereof our invention is set forth in the following claims.

We claim:

l. The method of preparing an insulated surgical suture which comprises: spinning not less than 19 stainless steel filaments having a diameter of less than 0.0018 inch each into a flexible multifliament wire, anodically cleaning said wire, washing and rinsing said wire, coating said wire with a thin layer of polytetratluoroethylene, stripping sections of the wire corresponding to the ends ot individual sutures, src-cutting and fusing the wire in said stripped sections into individual lengths having unsplaycd ends thus forming sutures, and crimping a surgical needle to each end of the thus formed sutures.

2. The method of preparing an insulated surgical suture which comprises: spinning not less than i9 stainless steel filaments having s diameter of less than 0.0018 inch each into a flexible multiillament wire, anodicsily cleaning said wire, washing with a volatile dilute mineral acid, and rinsing said wire in water, then drying, wrapping said wire with a thin layer of polytetrafluoroethylene, fusing the wrapping to a thin sheath layer of polytetrafluoroethylene, stripping sections of the wire corresponding to theends of individual sutures,passing a low voltage current throughthe wire of such magnitude that the wire is fused to formtwo separate beaded unsplayed ends,

the individual lengths having unsplayed ends thus forming sutures, and crimping a surgical needle to each end of the thus formed sutures.

3. A stainless steel surgical suture comprising: at least 19 individual surgically clean stainless steel filaments in conductive contact with each other over the entire length of the suture, each -filament with a diameter from about 0.0011 to about 0.0018 inch, and of a configuration selected from the lfollowing:

Construction Turns per Inch where -the construction column shows first the num-ber of strands in the suturel second tbe number of filaments (or ends) in each strand, and third the diameter of each filament in inches, and with the twist direction of the filaments in cach strand opposed to the direction of twist of the strands in the suture, and an eyeiess surgical needle attachedto and in conductive contact with the surgically clean stainless steel filaments at at least one end of the suture.

4. A stainless steel surgical suture comprising: at least 19 individual surgically clean stainless steel filaments in conductive contact with each other over the entire length of the suture, each filament with a diameter from about 0.0011 to about 0.0018 inch, and an eyeiess surgical ncedle attached to and in conductive contact with the surgically clean stainless steel filaments at at least one end of the suture.

5. A stainless steel surgical suture comprising: at least 19 individual surgically clean stainless steel filaments in conductive contact with each other over the entire length of' the suture, each filament with a diameter from about 0.0011 to about 0.0018 inch, and of a configuration selected from the following:

Construction Turns per liteit die attached to and in conductive contact with the surglcally clean stainless steel filaments at at least one end of the suture,.and a single impermeable polytetrafluoroethylene coating on the whole exterior surface of the twiisted filaments and insulating the wire, except at the en s.

6. An insulated needled electrically conductive surgical suture comprising: the stainless steel suture of claim 5 having exposed wire ends, and one eyeiess surgical needle attached at each end of the steel filaments, and in contact therewith.

7. in a suture structure, a non-resorbable, nonoxidiz ing flexible conductor of surgically clean stainless steel, a non-conductive cover of polytetrafluoroethylene for said conductor on the surface thereof over a substantial portion of its length, but leaving bare both of the termini and an eyeiess needleA attached to atleast one of the bare termini, said conductor comprising at least 19 surgically clean stainless stoel filaments in-conductive contact with cach other over the-entire lcngth of the suture, cach filament having a diameter from` about 0.0011 to about 0.0018 inch.

Ref'renccs Cltcd in the lc of this patent UNITED STATES PATENTS Morton Oct. 20, 1925 Hirsch ct al May 22, 1962 Nixon Sept. 18, 1962 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION,

Patent. No. 3,125,095 vMarch 17, A1964 David Kaufman et a1.

It is herebyv certified `that error appears in'the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 51, for "he" read the line O, for "eyeglass" read eyeless Signed and sealed this 8th day of September 1964.

(SEAL.) Attest:

ERNEST w.- swIDR 4EDWARD J. BRENNER Altcsting Officer Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,125,095 March 17, 1964 David Kaufman et al.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 51, for "he" read the line O, for "eyeglass" read eyeless Signed and sealed this 8th day of September 1964.

(SEAL) Attest:

ERNEST w, swIDER lEDWARD J. BRENNER Amsstng Officer Commissioner of Patents 

3. A STAINLESS STEEL SURGICAL SUTURE COMPRISING: AT LEAST 19 INDIVIDUAL SURGICALLY CLEAN STAINLESS STEEL FILAMENTS IN CONDUCTIVE CONTACT WITH EACH OTHER OVER THE ENTIRE LENGTH OF THE SUTURE, EACH FILAMENT WITH A DIAMETER FROM ABOUT 0.0011 TO ABOUT 0.0018 INCH, AND OF A CONFIGURATION SELECTED FROM THE FOLLOWING: 